1. Field of the Invention
The present disclosure generally relates to imaging and, more particularly, to an apparatus and method for enlarging an object included in image data, and storage medium therefor.
2. Description of the Related Art
There is an apparatus for printing a full color image by using the four process colors (color planes) including C (cyan), M (magenta), Y (yellow), and K (black). In the print process performed by this apparatus such as image data transfer onto a recording medium, a color plane deviation (plane deviation) may arise. Such a plane deviation may cause the color of paper (print medium) to be seen at the boundary between adjacent objects each including a different color plane. This phenomenon is referred to as a white spot.
For example, suppose printing of image data including a black color plane object (K object) and a magenta color plane object (M object) adjacent to the K object. The image data is ideally printed without plane deviation, as illustrated in FIG. 1A. However, in the print process of the relevant image data, if the black plane (K plane) shifts to the left of the magenta plane (M plane), a white spot arises between the K and the M objects, as illustrated in FIG. 1B.
Trapping processing is a technique for preventing a white spot. The trapping processing enlarges one color plane object included in the image data toward the other color plane object adjacent to the one color plane object. With the trapping processing, one color plane object and the other color plane object overlap with each other at the boundary between the two objects in advance. When the image data having undergone the trapping processing is ideally printed without plane deviation, the K and the M objects overlap with each other at the boundary of the two objects, as illustrated in FIG. 1C. On the other hand, if a plane deviation arises in the print process of the image data having undergone the trapping processing, the image data is printed as illustrated in FIG. 1D. Specifically, since the K object has been enlarged toward the M object in advance, a white spot does not arise even if a plane deviation arises.
Japanese Patent Application Laid-Open No. 2004-122692 discusses a technique for allowing a user to set a pixel width, i.e., a width by the number of pixels (referred to as a trapping width) by which one color plane object is to be enlarged toward the other color plane object.
Suppose a case where a large trapping width is set in Japanese Patent Application Laid-Open No. 2004-122692. In this case, if the width of the K object is narrow, the M object is enlarged to protrude from the left-hand side of the K object, as illustrated in FIG. 1E. Accordingly, a color which is not originally present appears at the left-hand boundary of the K object, possibly resulting in image quality degradation. Such image quality degradation arises not only when a large trapping width is set but also when a plane deviation of the M object becomes larger toward the K object (to the left).